Encyclopedia of Evolution.pdf - Online Reading Center

ig bang
make nests with horizontal combs on tree boughs or rocks.
It is likely that A. mellifera evolved from bees with habits
similar to those still found in A. florea. When the dwarf bee
scout returns from a new food source, she performs a dance
on the horizontal surface of the comb in which the straight
run points directly toward the food. This intermediate evolutionary
step in the evolution of the bee dance has in fact been
observed.
Another necessary step in the evolution of the bee dance
would be for gravity (on the vertical honeycomb in the dark
hive) to substitute for light (on the horizontal honeycomb on
the rock or branch). A scientist performed an experiment in
which a light bulb was placed in a honeybee hive. When a
scout was dancing, the scientist turned on the light. The scout
then altered the direction of her waggle dance to align to the
light, rather than to gravity. Apparently the honeybee retains
a primitive instinct to align its dance to the Sun, an instinct
it has not used since it evolved the habit of making vertical
honeycombs in the dark.
The evolution of complex behavior patterns is slow and
gradual and has not been observed to occur over short periods
of time. However, as in the case of bee foraging behavior,
some behavior patterns that scientists believe to have been
present in the ancestors of honeybees can still be found, in
honeybees or their close relatives.
2. Fitness advantages of specific behaviors. The study
of the fitness advantages conferred by natural selection upon
behavior patterns is called sociobiology. Sociobiology has
been particularly successful at explaining the fitness advantages
of altruism, especially in social insects. Sociobiology
has often explained the evolution of fixed action patterns,
and of learning abilities. A central idea of sociobiology is that
an understanding of the evolutionary basis of behavior in one
animal species should provide insights into the behavior of
other species, including humans. As behavioral scientist Tim
Friend says, “No matter where you look, just about every
creature is obsessed with sex, real estate, who’s the boss, and
what’s for dinner.”
Sociobiology has proven controversial among scientists
particularly when sociobiologists have attempted to explain
the fitness advantage of specific human behavior patterns.
Examples include religion and the fear of strangers (see religion,
evolution of). Sociobiologists point to the universality
of these behaviors, and the fitness advantages that would
result from them. This implies, sociobiologists claim, that
the specific behavior patterns are genetically based. Sociobiologists
do not deny that learning and volition can modify or
override these genetically based behaviors. Critics of sociobiology
claim that natural selection has caused the evolution of
a human brain that is so large and flexible that its ability to
learn and modify human behavior far outweighs any residual
genetic influence. To the critics, human behavior results from
a genetically-based brain, but specific human behavior patterns
have no genetic basis (see essay, “How Much Do Genes
Control Human Behavior?”).
Each species evolves its own set of behavioral patterns.
Some behavioral patterns have evolved in more than one
species because these patterns allow communication that is
beneficial to more than one species. An example is Müllerian
mimicry (see mimicry) in which dangerous prey all share a
common set of warning coloration patterns (usually black
alternating with white, yellow, orange, or red). Warning coloration
alerts predators to leave these dangerous prey animals
alone. More than one animal species can also share the ability
to produce and recognize warning calls. Mammals have
been seen to respond to bird calls that indicate the presence
of a predator.
Behavior patterns may not be only a response to environmental
conditions, but can contribute to those conditions. If
some animals within a group learn a new behavior, it can give
them a fitness advantage; the behavior can spread through the
group, or the entire species, by a nongenetic learning process.
This newly acquired behavior creates a situation in which
there is a fitness advantage for any genetic variation that may
make that behavior easier or more effective. A bird may learn
to eat a new type of food, which is not an evolutionary modification.
However, any mutant birds that had a genetically
based preference for that new type of food, or beaks that
allowed them to eat it more efficiently, would be favored by
natural selection. This is gene-culture coevolution.
One of the greatest difficulties in studying the evolution
of animal behavior is that humans tend to impute consciousness,
volition, even intelligence, to practically every action,
not only to the behavior of animals but even to storms and
earthquakes. Even though scientists have demonstrated that
many complex animal behaviors result from fixed action patterns
modified by learning, human observers cannot help but
imagine that these behaviors are conscious and purposeful.
Evolutionary philosopher Daniel Dennett has focused attention
on the conditions that would favor the evolution of true
consciousness, as opposed to behavioral patterns that simply
appear conscious to human observers.
Further Reading
Alcock, John. Animal Behavior: An Evolutionary Approach. Sunderland,
Mass.: Sinauer Associates, 2001.
Dennett, Daniel. Kinds of Minds: Towards an Understanding of Consciousness.
New York: Basic Books, 1997.
Friend, Tim. Animal Talk: Breaking the Codes of Animal Language.
New York: Free Press, 2004.
Lorenz, Konrad. King Solomon’s Ring: New Light on Animal Ways.
1952. Reprint. New York: Routledge, 2002.
big bang See universe, origin of.
biodiversity Biodiversity is the total number of species
in the world, or within any limited place. Biodiversity is the
product of evolution. Evolutionary scientists are interested in
how the patterns of biodiversity differ from place to place,
and how they have changed over the history of the Earth,
because this gives them insight into how the evolutionary
process works.
The most general pattern of biodiversity is that the
places on the Earth, and the times in Earth history, that have
the most species are those with the highest temperature and
greatest amount of moisture. Today this is represented by the